The spectral composition of the X-rays coming from an X-ray tube depends on the acceleration voltage of the electron beam. As the different sorts of tissue in a living body have different absorption properties depending on the energy of the X-rays, this effect can be used to differentiate between different tissue compositions and thus allow more specific diagnosis of various pathological situations. Ideally, in computed tomography every other frame can be taken with a different energy level and the type of tissue can be examined in addition to the standard 3D-picture.
WO 2012 080 899 A1 (US 2013/0251108) describes a power supply unit for an X-ray radiation source comprising a high voltage generator for providing a basic current for the operation of an X-ray tube, a waveform generator and a pulse transformer for providing superimposable voltage peaks and a control unit for generating a counterbalance at an input of the pulse transformer to prevent saturation effects. Providing different reference waveform patterns leads to the prevention of overshooting and ringing.
In the described solution, the acceleration voltage of the electron beam is the superposition of the DC voltage created by the main high voltage generator and a high voltage pulse pattern created by a control unit and waveform generator in conjunction with the pulse transformer. The waveform generator creates a pulse pattern at low voltages and high currents. The pulse transformer converts this to a pulse pattern at high voltages and low currents and superposes it with the high DC voltage of the main generator.
DE 42 04 092 A1 describes spool bodies used with coil chambers for coiled products e.g. high voltage transformers. A therein described spool body with at least one coil chamber is used for coiled products especially for high voltage transformers. The therein described passage between the chamber inner wall and the bottom of the chamber is adapted to the geometry of the coil.
The pulse transformer has to isolate the large voltage difference between the primary winding linked to the low voltage circuit of the waveform generator and the secondary winding linked to the high voltage circuit of the main generator. The operating frequency of the pulse transformer is determined by the duration of the pulse pattern defined by the application requirements outlined above. Therefore, it is not possible to reduce the size of the pulse transformer by increasing its operating frequency as can be done e.g. for the high voltage transformer in the main generator. Therefore, the high voltage isolation of the pulse transformer has to be designed with special care to avoid any unnecessary increase of its dimensions.